Method for determining start and end points of regeneration of diesel soot-filtering device

ABSTRACT

Disclosed herein is a method for determining start and end points of regeneration of a diesel soot-filtering device, which measures a value (hereinafter, referred to as “flow resistance value”) obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas so as to determine the degree of accumulated amount of soot, so that the start and end points of a compulsory regeneration of the soot-filtering device can be easily determined.

RELATED APPLICATION

The present application is a continuation-in-part of U.S. patent application Ser. No. 11/142,116, filed Jun. 1, 2005, which claims priority to Korean Application No. 10-2004-0039431, filed Jun. 1, 2004. The disclosure of each of the above-cited applications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for determining start and end points for regeneration of a diesel soot-filtering device, and, in particular, a method in which a value (hereinafter, referred to as “flow resistance value”) is obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas to determine the degree of accumulated amount of soot, so that the start and end points of compulsory regeneration of the soot-filtering device can be more easily determined.

2. Background of the Related Art

Currently, efforts have been made for the development of a diesel soot-filtering device (see FIG. 2) so as to cope with a EURO-IV regulation. Modifications to many systems are required in order to conform to such regulation. Since it is difficult to satisfy the requirements of this regulation only with an existing oxidation catalyst, a novel diesel soot-filtering device is being developed.

Specifically, in case of a diesel motor vehicle, a diesel soot-filtering device may be not installed in a vehicle having a load capacity of less than 1.7 tons so as to satisfy the requirements of the EURO-IV regulation. On the contrary, the diesel soot-filtering device must necessarily be installed in a vehicle having a load capacity of more than 1.7 tons to satisfy them.

In order for a diesel motor vehicle to be equipped with a diesel soot-filtering device, a large amount of engine data and vehicle data must be secured, and a sufficient time period for mapping such data is required. How captured soot is effectively burned for continuous reuse is one factor for the mounting of the diesel soot-filtering device. Minimum and high-priority test variables to be previously taken into consideration in order to develop and equip a diesel soot-filtering device are as follows:

(1) Whether the temperature of exhaust gas has risen due to post-injection of fuel (including advance/retard?)

(2) Soot compulsory regeneration strategy according to engine condition

(3) Checking both the loaded amount of soot and the start and end points of soot compulsory regeneration

(4) Technology for preventing uncontrolled burning, etc.

As mentioned above, in order to manufacture and sell a diesel motor vehicle, it must meet certain durability and evaluation tests (European Evaluation Mode: EC mode, US Evaluation Mode: FTP-75 mode). Further, it is required that various development logics conform to given conditions and situations on a real roadway, including basic logic, error logic, soot compulsory regeneration logic, so as to prevent unexpected trouble.

Sufficient data is needed for test variables in all the cases as described above. After grasping the problems associated with the items (1), (2) and (4), mapping and test data must be retained sufficiently. But in case of the item (3), although sufficient test data is retained, accurate amount and the accumulated extent of soot must be checked in order to usefully utilize such data. To this end, currently, the amount of soot accumulated actually in a real vehicle and an engine can be measured only by using a scale without other separate methods.

Consequently, during the test of the real vehicle and the engine, in order to check the start point of soot compulsory regeneration, it is required that the amount of soot currently accumulated within the soot-filtering device be measured using a scale after removing a corresponding soot-filtering device, followed by re-mounting it so as to proceed the test.

However, it is nearly impossible to carry out such a process since the weight of the soot-filtering device generally reaches 12 to 15 kg, and the soot weighs only approximately 1 to 12 g which is in a relatively very small amount as compared to the weight of the device, resulting in a significant decrease in accuracy. In addition, since the weight of the soot varies even in the case where foreign substances adhere to the outer appearance of the soot-filtering device while traveling, it is impossible to accurately measure the weight of the soot in real time.

The same difficulties arise in an engine test. However, the engine test undergoes an easier process than that in the vehicle test. Similarly, in this case, the amount of soot currently accumulated within the soot-filtering device is measured using a scale after removing the soot-filtering device, which is the same as in the vehicle test. That is, the weight of a corresponding soot-filtering device is measured using a scale after it is removed, and then the device is re-mounted so as to proceed with the test. Resultantly, in the case where such a test is repeatedly performed, the development period will be greatly extended as well as reliability of data measured will be significantly degraded.

Since it is difficult to accurately measure the amount of soot accumulated in the diesel soot-filtering device, the accurate start point of regeneration for the accumulated soot within the device cannot be set. A current regeneration logic of the diesel soot-filtering device is designed such that a post-injection is used to regenerate the soot at 600□ only in a condition mode beyond a certain condition in view of various variables such as water temperature (over 50°), engine rpm (over 2000 rev/min), vehicle speed, etc.

However, there remains a need for a method which can accurately identify the amount of soot accumulated in the diesel soot-filtering device prior to regeneration and post completion of the regeneration. Resultantly, since there is not a method for determining how much soot has been accumulated in the diesel soot-filtering device, and up to which level the soot can be eliminated after regenerating the soot at a given temperature, a situation may occur where it is impossible to identify the conditions within the soot-filtering device. This results in an unnecessary waste of fuel, an aggravation in fuel consumption ratio, and a reduction in durability due to frequent regeneration of the soot-filtering device.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method for determining start and end points for regeneration of a diesel soot-filtering device, which measures a flow resistance value obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas, depending upon the amount of soot accumulated in the soot-filtering device regardless of the condition of an engine and a vehicle so as to determine the degree of accumulated amount of soot and the measured corresponding flow resistance value. A software basis may be prepared and the start and end points for compulsory regeneration of the soot-filtering device can be easily determined through the later measurement of the flow resistance value in a real vehicle.

In exemplary embodiments of a method for determining start and end points for regeneration of a diesel soot-filtering device includes measuring a flow resistance value (i.e., a value obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas) which varies depending upon the amount (SL) of soot accumulated in the soot-filtering device regardless of the condition of an engine and a vehicle; storing the amount (SL) of accumulated soot and the measured corresponding flow resistance value (FR1) in a storage/computation means; setting the flow resistance value (FR1) corresponding to the previously stored amount (SL) of soot as a reference of the start point of compulsory regeneration of the soot-filtering device; measuring a flow resistance value (FR2) in a real vehicle, and at the same time, computing and identifying the amount (SL) of soot corresponding to the measured flow resistance value (FR2) through the storage/computation means; and comparing/computing the flow resistance value (FR2) in the real vehicle and the corresponding flow resistance value (FR1) of the identified amount (SL) of soot through the storage/computation means, whereby the start and end points of a compulsory regeneration of the soot-filtering device are determined, and simultaneously whether the soot-filtering device is compulsorily regenerated is determined.

In a preferred embodiment, the storage/computation means is an ECU, compares the flow resistance value (FR2) measured in a real vehicle with the previously stored corresponding flow resistance value (FR1), and when the measured flow resistance value (FR2) is identical to the previously stored corresponding flow resistance value (FR1), determines that a current regeneration start point is the start point of the compulsory regeneration while compulsorily regenerating the soot-filtering device.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart illustrating a method for determining start and end points for regeneration of a diesel soot-filtering device according to an embodiment of the present invention;

FIG. 2 is a schematic view illustrating a diesel soot-filtering device according to the accumulation of mileage;

FIG. 3 is a graph illustrating a variation in flow resistance value (Del.P/Volume Flow) in a vehicle over time at 6 g/L soot loading;

FIG. 4 is a graph illustrating a variation in flow resistance value (Del.P/Volume Flow) in a vehicle over time at 8 g/L soot loading;

FIG. 5 is a graph illustrating a correlation between an accumulated soot amount, i.e., soot loading and the flow resistance value; and

FIGS. 6 a and 6 b are graphs illustrating a variation in flow resistance value over time during the compulsory regeneration at soot loadings of 6 g/L and 8 g/L, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiment of the present invention with reference to the attached drawings.

Referring to FIGS. 1 and 2, a flow resistance value (i.e., a value obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas) which varies depending upon each amount (SL) of soot accumulated in the soot-filtering device regardless of the condition of an engine and a vehicle is measured. The process of measuring the flow resistance value may include: allowing an ECU to receive a signal output from a differential pressure sensor installed at the front and rear ends of the soot-filtering device so as to calculate a difference between pressures at the front and rear ends of the diesel soot-filtering device; allowing the ECU to receive a signal output from a sensor for detecting the intake air volume and the amount of fuel so as to measure the flow rate of exhaust gas; and dividing the calculated pressure difference at the front and rear ends by the measured flow rate of exhaust gas. The ECU of the present invention may include a processor, memory and associated hardware and software as may be selected and programmed by a person of ordinary skill in the art based on the teaching contained herein.

As shown in FIG. 3, the variation in a flow resistance value is represented as a sharp curve (red colored line) depending on engine rpm and other variables, but is represented as a more stable curve (blue colored line) after being subjected to filtering by the ECU. It can be seen from FIG. 3 that the traveling speed of the vehicle and the engine rpm vary momentarily, and air volume and fuel amount also vary every moment by being applied with a transient interval. But the flow resistance value exhibits a width of uniform variation, which nearly ranges from 0.030 to 0.035. This means that the amount of soot accumulated in the diesel soot-filtering device reaches approximately 6 g. The flow resistance value in a test vehicle shows a uniform range of nearly 0.030 to 0.035 while not varying easily depending on the external condition of a vehicle.

As shown in FIG. 4, the flow resistance value corresponding to 8 g/L soot loading is within a range between 0.0050 and 0.055 or so. Next, the each amount (SL) of accumulated soot and the measured corresponding flow resistance value (FR1) are stored in a storage and computation means, which may be, for example, the ECU described above, and the flow resistance value (FR1) corresponding to the previously stored amount (SL) of soot is set as a reference of the start point of a compulsory regeneration of the soot-filtering device. In this manner, in a state where the flow resistance value (FR1) according to each amount of accumulated soot has been previously stored in the ECU, when a flow resistance value (FR2) in a real vehicle is measured, it is possible to identify how much soot is accumulated in the real vehicle. That is, the flow resistance value (FR2) of a real vehicle is measured, and simultaneously, the amount (SL) of soot corresponding to the measured flow resistance value (FR2) is computed and identified by the ECU. Subsequently, the flow resistance value (FR2) of the real vehicle and the corresponding flow resistance value (FR1) of the identified amount (SL) of soot are compared with each other and computed by the ECU, so that the start and end points of a compulsory regeneration of the soot-filtering device are determined, and simultaneously whether the soot-filtering device is compulsorily regenerated is determined.

Resultantly, the flow resistance value measured under a real vehicle condition can be easily obtained through the data of the ECU, i.e., the previously stored flow resistance value. When monitoring the measured flow resistance value, it is possible to grasp a degree of accumulated amount of soot and the start and end points of regeneration of the diesel soot-filtering device.

More specifically, the ECU compares the flow resistance value (FR2) measured in a real vehicle with the flow resistance value (FR1) previously stored therein. When the measured flow resistance value (FR2) is identical to the previously stored flow resistance value (FR1), the ECU determines that a current regeneration start point is the start point of the compulsory regeneration while compulsorily regenerating the soot-filtering device.

In order to draw a linear graph as in FIG. 5, a soot-filtering device with an unknown amount of accumulated soot is installed in a vehicle, and then a flow resistance value corresponding to the amount of accumulated soot is obtained. When a linear graph is drawn, a soot-filtering device with an unknown amount of accumulated soot can be installed in a real vehicle, and then a flow resistance value corresponding to the amount of accumulated soot is obtained. Then, the amount of soot accumulated in the soot-filtering device can be accurately predicted.

In order to more effectively utilize the flow resistance value, it is calculated after being subjected to filtering in the ECU. Thereafter, the flow resistance value can be easily represented as a real number by multiplying the calculated flow resistance value by about 100.

Accordingly, when it is desired to regenerate the soot-filtering device based on a soot loading of 8 g/L, a flow resistance value of a real vehicle is measured to be within a range from 0.050 to 0.055. In this case, the amount of soot corresponding to the measured flow resistance value is identified by the ECU. Further, when the flow resistance value of a real vehicle is identical to or greater than the previously stored flow resistance value through subsequent computation of the ECU, the ECU starts to perform a compulsory regeneration of the soot-filtering device.

Referring to FIG. 6 a, it can be seen from the graph that almost all of accumulated soot is not burnt until about 1200 seconds needed for compulsory regeneration is spent under a traveling condition of a corresponding vehicle during the compulsory regeneration at a soot loading of 6 g/L. Referring to FIG. 6 b, it can be seen from the graph that it is necessary to set combustion time period of about 800 seconds so as to satisfy the compulsory regeneration requirements during the compulsory regeneration at a soot loading of 8 g/L.

Consequently, as shown in FIGS. 6 a and 6 b, the total time period required for the compulsory regeneration of the soot-filtering device can be determined by soot loading. Supposing that the amount of soot loaded within the soot-filtering device is regenerated in a unit of g, its flow resistance value is set as the start point of soot compulsory regeneration of ECU logic. Then, when a flow resistance value being monitored is shown as a value in excess of the flow resistance value previously stored in the ECU, it becomes possible to obviously determine how long the compulsory regeneration is needed and when the compulsory regeneration will terminated.

As described above, according to a method for determining start and end points of regeneration of a diesel soot-filtering device of the present invention, a flow resistance value obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas is measured so as to determine a degree of accumulated amount of soot and the measured corresponding flow resistance value, so that the amount of soot loaded in the soot-filtering device can be easily grasped and the start and end points of a compulsory regeneration of the soot-filtering device can also be easily determined based on the amount of soot loaded only through the later measurement of a flow resistance value in a real vehicle.

Further, the inventive method can be employed as a software key for the compulsory regeneration of the diesel soot-filtering device, and may be utilized as a method for controlling an engine, a method of predicting the time point for fuel amount determination and fuel injection by judging the amount of soot accumulated in the soot-filtering device.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. 

1. A method for determining start and end points for regeneration of a diesel soot-filtering device, comprising the steps of: measuring a flow resistance value varying depending upon an amount (SL) of soot accumulated in the soot-filtering device regardless of conditions of an engine and a vehicle; saving the amount (SL) of accumulated soot and the measured corresponding flow resistance value (FR1); setting the flow resistance value (FR1) corresponding to the saved amount (SL) of soot as a reference of the start point of a compulsory regeneration of the soot-filtering device; measuring a flow resistance value (FR2) in a real vehicle, and at the same time, computing and identifying the amount (SL) of soot corresponding to the measured flow resistance value (FR2); and comparing the flow resistance value (FR2) in the real vehicle and the corresponding flow resistance value (FR1) of the identified amount (SL) of soot, whereby the start and end points of a compulsory regeneration of the soot-filtering device are determined, and simultaneously whether the soot-filtering device is compulsorily regenerated is determined.
 2. The method of claim 1, wherein: said saving comprises storing data in a storage and computation means; said computing and identifying amount (SL) is performed through said storage and computation means; and said comparing of flow resistance values comprises computing and comparing said valves through said storage and computation means.
 3. The method according to claim 2, wherein the storage and computation means is an ECU, compares the flow resistance value (FR2) measured in a real vehicle with the previously stored corresponding flow resistance value (FR1), and when the measured flow resistance value (FR2) is identical to the previously stored corresponding flow resistance value (FR1), determines that a current regeneration start point is the start point of the compulsory regeneration while compulsorily regenerating the soot-filtering device. 